Investigation of the Wettability and the Heat Transfer on Laser-Manufactured Complex Surfaces during Vapour Condensation at Saturated and Superheated Condition

该项目的主要任务是利用激光制造技术系统地、选择性地改变过冷基底的表面质量，从而显着改善蒸汽冷凝过程中的散热性能。应该指出的是，与未修改的表面相比，在相同的操作条件下实现了散热的增加。在拟议的研究项目的框架中，打算使用光滑的非结构化参考表面以及由铝和铜制成的几个微结构化表面。对于扩大接触角，除了应用激光制造技术外，还对表面进行电化学处理。通过这一步骤，将在表面上实现纳米结构，这将导致液壁边界处的表面能降低和接触角增大，从而最终实现传热强化。通过实验，确定可以显着影响整个冷凝过程的影响因素（接触角/滞后、表面粗糙度、操作压力等），将通过传热和表面润湿的时空高分辨率测量及其与形貌的相互依赖性来确定将显示更改。此外，纳米微米结构对传热的贡献以及润湿特性应使用测量值进行数学建模，并应使用现有文献和实验数据进行验证。

The main task in this project is to systematically and selectively modify the surface quality of sub-cooled substrates by means of laser manufacturing technology, such that a significant improvement in heat dissipation during steam condensation is achieved. It should be noted that, compared with non-modified surfaces, the increase in heat dissipation is achieved at equivalent operating conditions.In the frame of the proposed research project it is intended to use a smooth, unstructured reference surface as well as several microstructured surfaces made of aluminum and copper. With regard to the contact angle enlargement, the surfaces are subjected to an electrochemical treatment in addition to the application of the laser manufacturing technique. Through this step, a nanostructuring is to be achieved on the surfaces, which should lead to reduced surface energy and larger contact angles at the liquid-wall boundary, in order finally to achieve an intensification of the heat transfer.From the experiments, determining influencing factors (contact angle / hysteresis, surface roughness, operating pressure, etc.), which can significantly influence the entire condensation process, will be identified by temporally and spatially high-resolved measurements on heat transfer and surface wetting and their interdependencies with respect to topography changes will be shown. Furthermore, the contribution of nano-micro-structures on heat transfer together with the wetting characteristics should be modelled mathematically by using of measured values and should be validated with the available literature and experimental data.